We will investigate the potential of photodynamic therapy for treatment of bronchogenic carcinoma. This will be accomplished by combining the phototoxicity of hemato-porphyrin-derivative (HPD) and a light delivery system designed for a flexible fiberbronchoscope. HPD is a chemical preferentially concentrated by neoplastic cells in animals and humans. It is a useful tumor marker, emitting a characteristic salmon-red fluorescence upon exposure to blue light. Furthermore, as a potent photodynamic agent, it produces cellular damage and death after exposure to light of sufficient dose and appropriate wavelength. Following our recent development of a clinically useful photoelectric bronchoscopic detector for the endoscopic localization of HPD-containing in situ and early invasic bronchogenic carcinoma, our attention is now directed toward designing a bronchoscopic therapeutic system for treatment of cancer. Wavelength, light intensity, and exposure time must be accurately measured and optimized to obtain maximum oncocidal effect with least toxicity to surrounding normal tissue. Preliminary assessment of the optimum wavelength and light dosimetry (intensity and time) to produce cell death will be done with cancer cell cultures. Cell fractionation studies will be used to measure the relative tumor penetration by light of various wavelengths and assess the photoxicity to surrounding normal tissue. Tumor specific transplantation immunity after photodynamic therapy will also be examined in this model. These data will then be used to design and build a therapeutic bronchoscopic system for treatment of bronchogenic carcinoma the effectiveness and photoxicity of which will be determined in a canine tumor model.